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Dose–response relationship in lethal and behavioural effects of different insecticides on the paras


Chemosphere 54 (2004) 619–627 www.elsevier.com/locate/chemosphere

Dose–response relationship in lethal and behavioural e?ects of di?erent insecticides on the parasitic wasp Aphidiu

s ervi
N. Desneux *, H. Rafalimanana, L. Kaiser
Laboratoire de Neurobiologie Compare des Invertbrs, INRA, BP 23, 91440 Bures-sur-Yvette, France e e e Received 18 February 2003; received in revised form 31 July 2003; accepted 3 September 2003

Abstract Neurotoxic insecticides are widely used for crop protection and behavioural perturbations can be expected in surviving bene?cial insects, including parasitoids of pest insects. The present study aims to investigate the relationship between the dose of insecticide parasitoids have been exposed to, and the subsequent ability of these parasitoids to respond to host-related cues. A four-armed olfactometer, a design widely used to observe orientation responses in various insects and parasitoids in particular, was chosen to investigate the dose–response relationship. The species studied was Aphidius ervi, a relatively generalist parasitoid of aphids, and commercialised for biological control and integrated pest management. Active ingredients with similar and di?erent modes of action on the nervous system were compared: a pyrethroid (lambda-cyhalothrin), an organophosphate (chlorpyrifos), a carbamate (pirimicarb) and a carbamyltriazole (triazamate). Adult females were exposed to dry residues on glass for 24 h. LD50 were calculated and predicted a high risk of mortality at the ?eld application rate. The e?ect of ?ve increasing residual doses of each active ingredient was tested on responses to plant-host odour in the olfactometer, from sublethal doses to LD50 , and up to LD70 for some products. It appeared that none of the doses of lambda-cyhalothrin, chlorpyriphos and pirimicarb had any e?ect on A. ervi responses to the odour from the aphid-infested plant (Myzus persicae on oilseed rape). But for triazamate, a signi?cant dose–behavioural response was quanti?ed and attraction to the odour was no longer signi?cant in females surviving the LD50 . The possible explanations for the presence or absence of e?ect, depending on the insecticide are discussed. ? 2003 Elsevier Ltd. All rights reserved.
Keywords: Aphid parasitoid; Host location; Olfactometer; Sublethal e?ect; Pesticide

1. Introduction Many natural enemies of phytophagous insects are Hymenopterous parasitoids. They are characterised by a parasitic larval development causing the death of the host. By reducing the population of their hosts, they can help to limit insect pest damage and, in some instances, prevent the outbreak of pests (Van Driesche and Bellows, 1996). They are important organisms for biologi-

Corresponding author. Tel.: +33-1-6929-8767; fax: +33-16907-5054. E-mail address: desneux@jouy.inra.fr (N. Desneux).

*

cal control. Among the biotic factors of pest mortality, insect parasitoids cause the strongest mortality (mortality compiled for 78 pest species, Hawkins et al., 1997). However, crop protection is mostly based on broad spectrum chemical insecticides that are noxious to bene?cial insects (Haskell and McEwen, 1998). For instance, pest resurgence or increase in populations of secondary pests can occur as a result of death or perturbation of bene?cial arthropods by pesticides (Hardin et al., 1995; Longley et al., 1997). Parasitoids can be exposed to pesticides through direct exposure to spray droplets (Jepson, 1989), or to residues on the crop foliage when foraging for hosts (Jepson, 1989; Longley and Jepson, 1996a,b) or through

0045-6535/$ - see front matter ? 2003 Elsevier Ltd. All rights reserved. doi:10.1016/j.chemosphere.2003.09.007

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dietary exposure through feeding on contaminated water droplets, nectar, or honeydews (Longley and Stark, 1996). Indirect exposure during the development in the host can also occur (Sss, 1983; Hsiech and Allen, u 1986; Longley, 1999). Exposure to low doses of insecticide residues is highly probable due to the widespread use of pesticides (Brown, 1989) and could induce sublethal e?ects in contaminated surviving insects. Sublethal e?ects are particularly expected on the behaviour of insects exposed to neurotoxic insecticides (Haynes, 1998), i.e. the majority of insecticides. Parasitoids spend a signi?cant proportion of their adult life searching for hosts. Host searching behaviour involves orientation to host and host-plant odours (Vinson, 1998). From the detection of odours to associated behaviours, olfaction is entirely dependent on nervous transmissions, which are targeted by neurotoxic insecticides through di?erent modes of action. The most common targets are (1) the voltagesensitive sodium channel on neuron membranes, whose openings are prolonged by pyrethroids (Soderlund and Bloomquist, 1989); (2) the acetylcholinesterase, which is inhibited by organophosphorous insecticides, carbamates (Fukuto, 1979) and carbamyltriazoles (Padilla, 1995); (3) the Gaba receptor, which is inhibited by organochlorous insecticides, and (4) the nicotinic acetylcholine receptors inhibited by the family of the neonicotinoids (Masuda et al., 2001) or activated by the family of spinosyns (Salgado, 1997). Therefore, insecticides may interfere with olfaction, depending on the mode of action and level of exposure. Few data are available on sublethal e?ects of pesticides on the orientation behaviour of insects. For example in honeybees, sublethal doses of insecticides have been shown to disturb the homing-?ight (Vandame et al., 1995) and odour learning (Abramson et al., 1999; Decourtye and Pham-Delgue, 2002). Orientation to sex e pheromone is disturbed by permethrin in pink bollworm moth, Pectinophora gossypiella (Haynes and Baker, 1985). Komeza et al. (2001) demonstrated that the behavioural response of the parasitoid, Leptopilina boulardi to host chemicals could be disturbed by a low dose of chlorpyrifos. This insecticide has also been shown to alter sex pheromone communication in Trichogramma (Delpuech et al., 1998). An increased response to hosthabitat odour after exposure to chlorpyrifos was also described by Rafalimanana et al. (2002). Deltamethrin at a sublethal dose increased the arrestment behaviour of treated Trichogramma males responding to female pheromone (Delpuech et al., 1999). Trissolcus basalis females exposed to a low dose of this insecticide reduced their walking speed and the time spent on host-patches (Salerno et al., 2002). The dose–response relationship has not been investigated in these previous studies, but it is valuable to be able to predict the impact of a known pesticide residue

on the foraging behaviour. The aim of the present work was thus to investigate the potential relationship between the dose of insecticide to which a parasitic wasp is exposed and its subsequent ability to respond to hostrelated cues. The species studied was Aphidius ervi Haliday (Hymenoptera: Braconidae), a parasitoid commercially used to control several aphid species in greenhouses. Exposure to increasing doses of insecticide was used to establish the dose–mortality relationship and to produce surviving insects with di?erent levels of contamination. These insects were observed in a fourarmed olfactometer delivering the host-plant odour. This device is commonly used to observe olfactory responses in various insect species (e.g., aphids: Pettersson, 1970; parasitoids: Vet et al., 1983; De Jong and Kaiser, 1991; honeybees: Sandoz et al., 2000). The insecticides belonged to the most common families used for crop protection, and di?ered in their mode of action on the nervous system of insects: a pyrethroid, lambdacyhalothrin; a carbamyltriazol, triazamate; a carbamate, pirimicarb; and an organophosphorous, chlorpyrifos.

2. Material and methods 2.1. Insects A. ervi adults were provided by Biobest (Belgium). Prior to testing, in order to allow mating, parasitoids were introduced in a plexiglas box (length: 18 cm; weight: 12 cm; height: 7 cm) provided with honey solution (80%) and placed in an environmental chamber at 15 ± 1 °C, 65 ± 5% relative humidity, and light regime 12L:12D. 2.2. Insecticide solutions Active ingredients were used instead of commercial formulations, because the aim was to document e?ects of the neurotoxic molecules on the behaviour, without in?uence of adjuvant added in commercial products. They were provided by Cluzeau InfoLabo (Sainte-Foy-laGrande, France): lambda-cyhalothrin (certi?ed purity 89.3%), triazamate (certi?ed purity 97.0%), pirimicarb (certi?ed purity 99%) and chlorpyrifos (certi?ed purity 99.1%). Lambda-cyhalothrin was in the form of a gel, pirimicarb and chlopyrifos-ethyl in the form of crystals and triazamate in the form of a solution in cyclohexane. A preliminary experiment was run to determine the range of insecticide doses, by exposing insects to doses equal to recommended ?eld application rates (ACTA, 2002) until observing mortality rates lower than 100%. To establish the dose–mortality relationship, insects were exposed to seven doses increasing by a 2 factor for lambda-cyhalothrin and triazamate, and to ?ve doses increasing by a factor 1.25 for chlorpyrifos and pirimi-

N. Desneux et al. / Chemosphere 54 (2004) 619–627 Table 1 Range of insecticide doses used to determine the LD50 and used subsequently in the olfactometer tests Active ingredients Lambda-cyhalothrin Doses used to determine LD50 (ng/cm2 ) 0.29? 0.58? 1.17? 2.34? 4.69? 9.37 18.75 Triazamate 1.05? 2.34? 4.68? 9.37? 18.75? 37.50 75.00 Pirimicarb 25.53? 31.92? 39.90? 49.87? 62.34? Chlorpyrifos 0.22? 0.28? 0.34? 0.43? 0.54?

621

?

Indicates doses used for the olfactometer tests.

carb. The ?rst ?ve doses of each insecticide were then used to evaluate their impact on the orientation behaviour (Table 1). Doses were expressed as ng of active ingredient per cm2 because we worked on the e?ects of residues. 2.3. Exposure of parasitoids to insecticide residues Insecticide solutions (with acetone or cyclohexane) were applied in glass tubes (length: 9.3 cm; diameter: 2.3 cm; internal surface: 67.4 cm2 ). Pure acetone was used as control for lambda-cyhalothrin, pirimicarb and chlorpyrifos and cyclohexane for triazamate because it was already diluted in cyclohexane in commercial form. To get a homogeneous deposit, we introduced 200 ll of solution, which allowed a total coverage of the internal surface of the tube, and the tube was then manually rotated until no more droplets were seen on the glass wall. Tubes were left for 1 h at room temperature to ensure complete evaporation of the acetone (or cyclohexane) before introducing parasitoids. Both internal surface of the tubes and volume of solution being ?xed, it was then possible to express the quantity of insecticide residue per unit of surface. At the time of exposure, A. ervi adults were four day old (Biobest, Personal communication). Ten females were placed per tube, with two drops of honey on a small plastic strip. Tubes were closed with a ?ne nylon gauze to allow air circulation. Exposure was performed at 15 ± 1 °C, 65 ± 5% relative humidity, and under a 12L:12D photoperiod. The temperature was set at 15 °C to avoid mortality in the control tubes, so it was always lower than the 10% mortality recommended to evaluate insecticides toxicity (Hassan, 1998). We checked that parasitoids were active in the tubes. Four replicates of at least 30 wasps (3 tubes of 10 females) were carried out for each dose of each insecticide. After 24 h of exposure, the number of dead parasitoids was counted to determine the regression lines of mortality and thus the LD50 . The survivors were collected and placed individually in Petri dishes, until being observed in the olfactometer (within the 2 h following the end of exposure).

2.4. Behavioural test in the four-armed olfactometer Oriented responses towards aphid-infested plant odour were observed in a four-armed olfactometer (Fig. 1) (from Vet et al., 1983). Pressurised and humidi?ed air ?ew into the central chamber through four arms (200 ml/ min per arm) and was extracted from the centre of the chamber, so that four ?elds of equal area were established. The device was placed on a light-table providing a homogeneous ?uorescent light (800 lx), in a room at 25 °C (temperature ensuring both active locomotion and high odour release rate), and 70% RH. In our experiments, only one ?eld was odorised. The odour source was constituted by oilseed rape stems (kept in water) (Brassica napus var Goeland) with a total of seven to eight leaves infested by Myzus persicae Sulzer (Homoptera: Aphididae) (400–500 aphids after seven days of infestation). To deliver the odour into one of the four ?elds of the olfactometer, the corresponding arm was connected to an air-tight glass jar (height: 25 cm; diameter: 11 cm), containing the odour source.
Air Air

Parasitoid introduction tube / connection tube airflow

Observation chamber

Air Extraction 5 cm

Air + odour

Fig. 1. Four-armed olfactometer used for studying the orientation behaviour of parasitoids. Four identical air?ows (200 ml/ min), entering the crescent-shaped chamber of the olfactometer by its four arms, were sucked through a central extraction hole which created four contiguous but distinct ?elds. One ?eld was scented with an odour source and the other three were left unscented. To observe attraction to the odour, an individual parasitoid was placed at the centre of the chamber, and its orientation behaviour was recorded for 1 min.

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A female parasitoid was introduced into a vial connected to the centre of the four-armed olfactometer, of which it could walk out freely. Observations started when the female entered the chamber, and lasted for 1 min, which was su?cient to observe a signi?cant attraction to the odour (Desneux et al., 2000). The position of the female (?elds numbered clockwise from one to four) was recorded on a computer using an event recorder software ‘‘the Observer’’ (Noldus Information Technology, Wageningen, The Netherlands), allowing to compute the overall time spent in each ?eld. After approximately every 20 individual observations, the olfactometer was carefully washed with ethanol and the position of the odorised ?eld was changed. E?ect of the four pesticides was examined on the orientation responses of surviving females. On each day of experiment, all doses were tested alternately. Sample sizes are reported on the graphs. 2.5. Data analysis Determination of LD50 : Dose–mortality relationship was determined using the computer program WIN DL (CIRAD-CA/MABIS, Montpellier, France), based on probit analysis (Finney, 1971). To evaluate the impact of insecticide exposure on the orientation behaviour, two statistical analyses were carried out. First, to investigate the existence of a dose– response relationship, we carried out a logistic regression of the percentage of time spent in the odour as a function of the pesticide dose (S-Plus, Venables and Ripley, 1999). In this regression, the deviation of the observed data is calculated relatively to a linear model under the as-

sumption that there is no dose e?ect. Second, to detect any e?ect of a given dose, the Kolmogorov–Smirnov statistic was used to compare the time spent in the odorised ?eld between the control group and each treated group (S-Plus, Venables and Ripley, 1999). 3. Results 3.1. Dose–mortality relationship (Table 2) Linear regression of the dose–mortality relationship was ?tted to the observed data for all tested active ingredients, as indicated by the absence of signi?cant deviation between the observed and the expected data. Then LD50 was considered as valid. Mortality in all control groups was always inferior to 5%. The slope of the regression line indicates how fast mortality occurs with increasing doses. The highest value was observed for pirimicarb and the lowest for triazamate. All LD50 were signi?cantly di?erent (no overlapping of the con?dence intervals) and allowed a ranking of the insecticides in order of increasing toxicity: pirimicarb, triazamate, lambda-cyhalothrin and chlorpyrifos. The recommended ?eld rate of these active ingredients was always higher than the LD50 , from 15 to about 8000 times (ratio between recommended ?eld rate and LD50 , Table 2). For the olfactometer tests, the doses used induced 0.9 ± 2.6% to 71.6 ± 15.2% of corrected mortality (Abbott, 1925) for lambda-cyhalothrin, 5.7 ± 2.5% to 53.4 ± 11.2% of corrected mortality for triazamate, 11.0 ± 6.1% to 76.0 ± 7.0% of corrected mortality for pirimicarb and 8.7 ± 5.2% to 63.3 ± 8.8% of corrected mortality for chlorpyrifos (Fig. 2A–D).

Table 2 Dose–mortality relationship. LD50 (with inferior and superior limits of the 95% con?dence interval), statistical results of adjustment to the log-probit model, rate recommended in the ?eld on oilseed rape against M. persicae and ratio between recommended ?eld rate and LD50 , for four pesticide residues applied in glass tubes for exposure of A. ervi adults (for chlorpyrifos, the rates recommended against Ostrinia nubilabis on maize were used to calculate ratio because this pesticide is not used in France on oilseed rape) Active ingredients Inf lim < LD50 < sup lim (ng/cm2 ) 4:48 < 4:97 < 5:52 Equations of mortality linear regression and statistics Y ? ?2:30 ? 3:37X v2 ? 7:63; P ? 0:267 (df 6) Y ? ?3:03 ? 2:45X v2 ? 5:05; P ? 0:410 (df 6) Y ? ?9:27 ? 5:92X v2 ? 5:92; P ? 0:115 (df 4) Y ? 1:44 ? 4:41X v2 ? 5:53; P ? 0:137 (df 4) Recommended ?eld rates (g a.i./ha) 7.5 Ratio: recommended ?eld rates/LD50 15.09

Lambda-cyhalothrin

Triazamate

13:46 < 17:16 < 20:94

70

40.79

Pirimicarb

33:50 < 36:77 < 39:30

250

67.99

Chlorpyrifos

0:43 < 0:47 < 0:51

375

7978.72

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3.2. Dose–behaviour relationship All control groups exhibited a signi?cant attraction towards the aphid-infested plant odour (Friedman analysis of time allocation to the four ?elds: P < 0:05).
80
% of time in the odour field

The relative time spent in the odorised ?eld by females exposed to the di?erent doses of lambda-cyhalothrin (Fig. 2A) was not signi?cantly di?erent from that of control females (Kolmogorov–Smirnov: dose 0.29 ng/ cm2 : Z ? 0:22, P ? 0:188; dose 0.59 ng/cm2 : Z ? 0:14,
100 90 80 70 60 50 40 30 20 10 0

70 60 50 40 30 20 10 0 Control (n = 46) 0.29 (n = 44) 0.58 (n = 44) 1.17 (n = 47) 2.34 (n = 45) 4.69 (n = 45)

(A)
80
% of time in the odour field

**

60 50 40 30 20 10 0 Control (n = 39) 1.17 (n = 35) 2.34 (n = 34) 4.68 (n = 35) 9.37 (n = 36) 18.75 (n = 28)

(B)
80
% of time in the odour field

60 50 40 30 20 10 0 Control (n = 44) 25.53 (n = 47) 31.92 (n = 44) 39.90 (n = 43) 49.87 (n = 41) 62.34 (n = 41)

(C)
80
% of time in the odour field

60 50 40 30 20 10 0 Control (n = 43) 0.22 (n = 43) 0.28 (n = 43) 0.34 (n = 44) 0.43 (n = 39) 0.54 (n = 33) odour % mortality

(D)

Fig. 2. E?ect of ?ve doses (ng/cm2 ) of lambda-cyhalothrin (A), triazamate (B), pirimicarb (C) and chlorpyrifos (D) on the orientation behaviour of A. ervi females observed at the end of the exposure. Percentage of time (±SE) spent in the odorant ?ow ?eld after 1 min of observation (grey bars). Kolmogorov–Smirnov test: **, P < 0:001. The corrected mortality (±SE) associated with each dose is represented by the black curve.

Corrected mortality (%)

70

100 90 80 70 60 50 40 30 20 10 0

Corrected mortality (%)

70

100 90 80 70 60 50 40 30 20 10 0

Corrected mortality (%)

70

100 90 80 70 60 50 40 30 20 10 0

Corrected mortality (%)

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P ? 0:697; dose 1.17 ng/cm2 : Z ? 0:10, P ? 0:923; dose 2.34 ng/cm2 : Z ? 0:25, P ? 0:108; dose 4.69 ng/cm2 : Z ? 0:18, P ? 0:402). The logistic regression of the percentage of time spent in the odour as a function of the dose was not signi?cant (v2 ? 1:29; df 1; P ? 0:255) indicating the absence of signi?cant dose e?ect. The relative time spent in the odorised ?eld by females exposed to the ?rst four doses of triazamate (Fig. 2B) was not signi?cantly di?erent from that of control females (dose 1.17 ng/cm2 : Z ? 0:17, P ? 0:579; 2.34 ng/ cm2 : Z ? 0:26, P ? 0:134; 4.68 ng/cm2 : Z ? 0:28, P ? 0:091; 9.37 ng/cm2 : Z ? 0:26, P ? 0:116). Nevertheless, the relative time spent in the odorised ?eld by females exposed to the highest dose of triazamate, 18.75 ng/cm2 , was signi?cantly di?erent from that of control females (Z ? 0:43, P ? 0:003). Additionally, we found a signi?cant logistic regression of the percentage of time spent in the odour as a function of the dose (v2 ? 6:16; df 1; P ? 0:013). The relative time spent in the odorised ?eld by females exposed to di?erent doses of pirimicarb (Fig. 2C) was not signi?cantly di?erent from that of control females (dose 25.53 ng/cm2 : Z ? 0:11, P ? 0:922; 31.92 ng/cm2 : Z ? 0:20, P ? 0:319; 39.90 ng/cm2 : Z ? 0:12, P ? 0:830; 49.87 ng/cm2 : Z ? 0:15, P ? 0:640; 62.34 ng/ cm2 : Z ? 0:11, P ? 0:922). The logistic regression of the percentage of time spent in the odour as a function of the pesticide dose was not signi?cant (v2 ? 0:35; df 1; P ? 0:554). The relative time spent in the odorised ?eld by females exposed to di?erent doses of chlorpyrifos (Fig. 2D) was not signi?cantly di?erent from that of control females (0.22 ng/cm2 : Z ? 0:12, P ? 0:938; 0.28 ng/cm2 : Z ? 0:16, P ? 0:625; 0.34 ng/cm2 : Z ? 0:22, P ? 0:171; 0.43 ng/cm2 : Z ? 0:16, P ? 0:632; 0.54 ng/ cm2 : Z ? 0:10, P ? 0:972). The logistic regression of the percentage of time spent in the odour as a function of the pesticide dose was not signi?cant (v2 ? 0:21; df 1; P ? 0:649). 4. Discussion 4.1. Dose–mortality relationship For each active ingredient tested, there was a good ?t between the observed dose–mortality relationship and the linear regression, so our experimental conditions gave reliable estimations of LD50 . Values allowed to rank the insecticides in order of increasing toxicity: pirimicarb, triazamate, lambda-cyhalothrin and chlorpyrifos, the latter being about 100 times more toxic than pirimicarb. However, it is not possible to use the LD50 to compare the sensibility of A. ervi to other parasitoid species, because almost no data are available in the literature. Indeed, the toxicity of insecticides to bene?cial

arthropods has always been estimated using mortality induced by the ?eld application rate. The estimation of LD50 was only recently recommended for parasitoids (Candol? et al., 2001). Our data indicated that recommended ?eld rates were always higher than LD50 for the four studied active ingredients. When testing commercial products, the ratio between the ?eld application rate and the LD50 , i.e. Hazard Quotient (HQ), gives an indication of the risk. This quotient is already used for evaluating the toxicity of pesticides to honeybees (EPPO, 1999). Although our LD50 were calculated for active ingredients, the ratio to the recommended ?eld rate does allow to compare the risk among the four tested insecticides. Using the ?eld recommended rates against aphids on oilseed rape (and against the European Corn Borer on maize for chlorpyrifos), ratios were equal to 15 for lambda-cyhalothrin (which means that 1/ 15 of the ?eld application rate will kill 50% of the A. ervi population), 41 for triazamate, 68 for pirimicarb and 7979 for chlorpyrifos, presenting the highest risk to A. ervi. Both toxicity and risk of chlopyrifos-ethyl to A. ervi were the highest compared to the other three insecticides. But for these three insecticides, comparison of LD50 on the one hand, and of the ratio on the other hand, gave inverse classi?cations. Ranking the ratios pointed out that lambda-cyhalothrin presented the lowest risk to A. ervi. 4.2. Dose–behaviour relationship For three of the four active ingredients tested: lambda-cyhalothrin, pirimicarb, chlopyrifos-ethyl, the orientation behaviour in the olfactometer was not changed in insects surviving to any doses of insecticides. Survival was not due to reduced exposure to residues, because the regular increase of mortality with increasing doses indicates a homogeneous exposure of the insects. Unaltered orientation behaviour in contaminated females can have two explanations: either the insecticide molecules did not alter the functions necessary for olfactory responses in the olfactometer, or surviving insects were less susceptible. As regards the ?rst explanation, considering the cellular and molecular targets of pyrethroids, organophosphorous and carbamate, e?ects on olfactory responses are expected. This has been veri?ed in a number of studies on pyrethroids and organophosphorous: different pyrethroids modi?ed olfactory learning in the honeybee (Taylor et al., 1987; Mamood and Waller, 1990; Abramson et al., 1999), and responses to sex pheromone in the parasitoid Trichogramma (Delpuech et al., 1999) and in a moth (Floyd and Crowder, 1981; Haynes and Baker, 1985). Chlorpyriphos-ethyl modi?ed responses of parasitoids to host and host-habitat odours (Komeza et al., 2001; Rafalimanana et al., 2002) and to sex pheromone (Delpuech et al., 1998).

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With regard to the second explanation, it implies a heterogeneity in susceptibility within the A. ervi population to insecticides. According to Croft (1990), tolerance to pesticides may occur as a direct result of the organism’s short- and long-term exposure to toxins in nature. Variable level of tolerance can re?ect di?erences in vigour or in genetically determined susceptibility to pesticides. The latter was reported in some other Hymenopteran parasitoid species (Hoy, 1990). Both sources of variability are likely in A. ervi. Vigour can vary according to characteristics that were not controlled precisely in our experiment, like size, stress and general physiological state. Genetic variability of sensitivity to insecticides may have resulted from the yearly incorporation of ?eld-collected females to the mass-reared strain (Biobest, Personal communication). Indeed exposure to various pesticides residues has been occurring for years under ?eld conditions and may select less susceptible A. ervi. In addition, the results obtained with A. ervi in a previous study supported the hypothesis of heterogeneous sensitivity to insecticides in A. ervi species. Indeed, we observed that the orientation behaviour of A. ervi was disturbed by a sublethal dose (LD0:1 ) of lambdacyhalothrin (Desneux et al., 2000), which was not found again in the present study. These contrasting results may be due to di?erences in insecticide sensitivity between the strains of A. ervi, which did not come from the same company. As third explanation, the experimental conditions of the test in the olfactometer may not be optimal to observe sublethal behavioural e?ects. This study was the ?rst attempt to use a four-armed olfactometer to characterise the e?ects of neurotoxic insecticides on olfactory responses of insects. The in?uence of some experimental parameters remains to be tested. For instance, a longer observation time might have revealed e?ects on odour habituation, as already shown in L. boulardi responding to patches of host odours after exposure to chlorpyrifos (Komeza et al., 2001). E?ects could concern other behavioural items than the time spent in the odorised ?ow, such as the walking speed, which decreased in the parasitoid T. basalis exposed to the pyrethroid deltamethrin (Salerno et al., 2002). We can also hypothesise that the nervous functions used by the insect to walk into the odour ?ow are relatively limited and were not a?ected by the insecticides tested, whereas the same insects exposed to the same doses of insecticide might not be able to perform in-?ight orientation to an odour source, a task which requires di?erent muscular and nervous input, and the ability to detect a lower odour concentration diluted into the insect’s environment. For instance, Haynes and Baker (1985) have demonstrated that a pyrethroid, permethrin, decreased the attractiveness of sex pheromone in a moth tested in a wind tunnel, but this sublethal e?ect did not occur when moths were close to the odour source, i.e. when placed in a higher odour concentration. Therefore,

although exposure to lambda-cyhalothrin, chlorpyrifos and pirimicarb did not have any e?ect on A. ervi orientation in the four-armed olfactometer, it might impair in-?ight orientation, or other types of behaviour involved in the host location and recognition (attack behaviour, etc. . .). Indeed, we observed an irreversible sublethal effect of chlorpyrifos within a few hours after the start of the exposure: some females were bending permanently their abdomen forward (as if attacking aphids), although they exhibited a normal orientation behaviour in the olfactometer. In contrast to lambda-cyhalothrin, chlorpyrifos and pirimicarb, A. ervi exposed to triazamate showed a reduction of the time spent in the odour ?ow proportional to the dose of residues, and the attraction to the odour was no longer signi?cant in insects exposed to the highest dose. The progressive e?ect of triazamate on the orientation behaviour is in accordance with the fact that mortality also occurred more progressively with increasing doses than with the other three insecticides tested. This suggests that triazamate would have a mode of action somehow di?erent from that of the other two inhibitors of acetylcholine esterase. Indeed, the action on a given target can di?er among active ingredients because of the various chemical functions which characterise insecticide molecules (Fukuto, 1979). Moreover, the insecticides often have secondary targets of actions (Soderlund and Bloomquist, 1989). Alternatively, a lack of tolerance to triazamate could explain that the orientation behaviour of A. ervi was more sensitive to triazamate than to the other three insecticides tested. Indeed, triazamate is considered as relatively recent, because it has only been commercialised in 1991 (Delorme et al., 2002). So it is probable that there is not yet any tolerance of parasitoids to this insecticide. In general, when insecticides have been used for a longer time (older), tolerance is more likely to have appeared. In M. persicae, known to rapidly develop resistance to insecticides, the ?rst case of resistant strain to triazamate was only recently reported (Foster et al., 2002), whereas resistant strains to organophosphorous, carbamates and pyrethroids appeared much before (Devonshire and Moore, 1982). In conclusion, as regards the behavioural e?ects of insecticide residues, this study was the ?rst attempt to establish a dose–behaviour relationship, using the fourarmed olfactometer, a device frequently used to observe olfactory orientation in various insects. It pointed out that among four active ingredients, only one induced a dose–response relationship whereas three had no e?ect on the orientation behaviour of surviving parasitoids. Further investigations are necessary to conclude on the possible reasons: observation parameters in the olfactometer, weak sensitivity of the responses developed in the olfactometer, or tolerance to older insecticides in surviving A. ervi.

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N. Desneux et al. / Chemosphere 54 (2004) 619–627 bamate andpyrethroid resistance in peach–potato aphids (Myzus persicae). Pestic. Biochem. Physiol. 18, 235–246. EPPO, 1999. Decision-making scheme for the environmental risk assessment of plant protection products. Bull. OEPP/ EPPO 23, 59–65. Finney, D.J., 1971. Probit Analysis. Cambridge University Press, Cambridge. Floyd, J.P., Crowder, L.A., 1981. Sublethal e?ects of permethrin on pheromone response and mating of male pink bollworm moths. J. Econ. Entomol. 74 (5), 634–638. Foster, S.P., Denholm, I., Devonshire, A.L., 2002. Fieldsimulator studies of insecticide resistance to dimethylcarbamates and pyrethroids conferred by metabolic- and target site-based mechanisms in peach–potato aphids, Myzus persicae (Hemiptera: Aphididae). Pest Manag. Sci. 58, 811–816. Fukuto, T.R., 1979. E?ect of structure on the interaction of organophosphorus and carbamate esters with acetylcholinesterase. In: Narahashi, T. (Ed.), Neurotoxicology of Insecticides and Pheromones. Plenum Press, New York and London, pp. 277–295. Hardin, M.R., Benrey, B., Coll, M., Lamp, W.O., Roderick, G.K., Barbosa, P., 1995. Arthropod pest resurgence: an overview of potential mechanisms. Crop Prot. 14, 3–18. Haskell, P.T., McEwen, P., 1998. Ecotoxicology––Pesticides and bene?cial organisms. Kluwer Academic Publishers, London. Hassan, S., 1998. Guideline for the evaluation of side e?ects of plant protection products on Trichogramma cacoeciae. Bull. IOBC/WPRS 21 (6), 118–128. Hawkins, B.A., Cornell, H.V., Hochberg, M.E., 1997. Predators, parasitoids and pathogens as mortality agents in phytophagous insect populations. Ecologist 78, 2145–2152. Haynes, H.F., 1998. Sublethal e?ects of neurotoxic insecticides on insect behavior. Annu. Rev. Entomol. 33, 149–168. Haynes, K.F., Baker, T.C., 1985. Sublethal e?ects of permethrin on the chemical communication system of the pink bollworm moth, Pectinophora gossypiella. Arch. Insect Biochem. Physiol. 2, 283–293. Hoy, M.A., 1990. Pesticide resistance in arthropod natural enemies variability and selection responses. In: Roush, R.T., Tabashnik, B.E. (Eds.), Pesticide Resistance in Arthropods. Kluwer Academic Publishers, Netherlands, pp. 203– 236. Hsiech, C.Y., Allen, W.W., 1986. E?ects of insecticides on emergence, survival, longevity, and fecundity of the parasitoid Diaeretiella rapae (Hymenoptera: Aphididae) from mummi?ed Myzus persicae (Homoptera: Aphididae). J. Econ. Entomol. 79, 1599–1602. Jepson, P.C., 1989. The temporal and spatial dynamics pesticide side-e?ects on non-target invertebrates. In: Jepson, P.C. (Ed.), Pesticides and Non-target Invertebrates. Intercept, Wimborne, pp. 95–127. Komeza, N., Fouillet, P., Boultreau, M., Delpuech, J.M., e 2001. Modi?cation, by insecticide chlorpyrifos, of the behavioral responses to kairomones of a parasitoid wasp, Leptopilina boulardi. Arch. Environ. Contam. Toxicol. 41, 436–442. Longley, M.A., 1999. A review of pesticide e?ects upon immature aphid parasitoids within mummi?ed hosts. Int. J. Pest Manage. 45 (2), 139–145.

Acknowledgements We wish to thank Minh-H Pham-Delgue for her a e scienti?c advices, Aude Couty for general discussions on the subject, Alfred Martin-Canadel for providing biological material and Annick Lacombe for linguistic corrections. This work bene?ted from a PNETOX grant from the French Ministry of the Environment and from a CETIOM/Aventis Crop Sciences grant. References
Abbott, W.S., 1925. A method for computing the e?ectiveness of an insecticide. J. Econ. Entomol. 18, 265–267. Abramson, C.I., Aquino, I.S., Ramalho, F.S., Price, J.M., 1999. The e?ect of insecticides on learning in the Africanized honey bee (Apis mellifera L.). Arch. Environ. Contam. Toxicol. 37, 529–535. ACTA, 2002. Index Phytosanitaire, 37th ed. ACTA, Paris. Brown, R.A., 1989. Pesticides and non-target terrestrial invertebrates: an industrial approach. In: Jepson, P.C. (Ed.), Pesticides and Non-target Invertebrates. Intercept, Wimborne, pp. 19–42. Candol?, M.P., Barrett, K.L., Campbell, P., Forster, R., Grandy, N., Huet, M.C., Lewis, G., Oomen, P.A., Schmuck, R., Vogt, H., 2001. Guidance document on regulatory testing and risk assessment procedures for plant protection products with non-target arthropods. In: SETAC/ESCORT 2 Workshop report, 21–23 March 2000, Wageningen. Croft, B.A., 1990. Arthropod Biological Control Agents and Pesticides. Wiley and Sons, New York. De Jong, R., Kaiser, L., 1991. Odor learning by Leptopilina boulardi, a specialist parasitoid (Hymenoptera: Eucoilidae). J. Insect. Behav. 4 (6), 743–750. Decourtye, A., Pham-Delgue, M.H., 2002. The proboscis e extension response as a laboratory method to assess the sublethal e?ects of pesticides on the honey bee. In: Devillers, J., Pham-Delgue, M.H. (Eds.), Estimating the Environmental e Impact of Chemicals to Honey Bees. Taylor and Francis, London, pp. 67–84. Delorme, R., Leroux, P., Gaillardon, P., 2002. Evolution des produits phytosanitaires  usages agricoles. III––Les inseca ticides-acaricides. Phytoma 548, 7–13. Delpuech, J.M., Gareau, E., Terrier, O., Fouillet, P., 1998. Sublethal e?ects of the insecticide chlorpyrifos on sex pheromonal communication of Trichogramma brassicae. Chemosphere 36 (8), 1775–1785. Delpuech, J.M., Legallet, B., Terrier, O., Fouillet, P., 1999. Modi?cation of the sex pheromonal communication of Trichogramma brassicae by sub-lethal dose of deltamethrin. Chemosphere 38, 729–739. Desneux, N., Noel, B., Kaiser, L., 2000. Sublethal e?ect of a pyrethroid on orientation behaviour of the parasitic wasp Aphidius ervi (Hymenoptera: Aphididae) in response to odour from oilseed rape infested by the aphid Myzus persicae. Bull. IOBC/WPRS 23 (9), 55–64. Devonshire, A.L., Moore, G.D., 1982. A carboxylesterase with broad substrate speci?city causes organophosphorus, car-

N. Desneux et al. / Chemosphere 54 (2004) 619–627 Longley, M., Jepson, P.C., 1996a. E?ects of honeydew and insecticide residues on the distribution of foraging aphid parasitoids under glasshouse and ?eld conditions. Entomol. Exp. Appl. 81, 189–198. Longley, M., Jepson, P.C., 1996b. The in?uence of insecticide residues on primary parasitoid and hyperparasitoid foraging behaviour in the laboratory. Entomol. Exp. Appl. 81, 259– 269. Longley, M., Stark, 1996. Analytical techniques for quantifying direct, residual, and oral exposure of an insect parasitoid to an organophosphate insecticide. Bull. Environ. Contam. Toxicol. 57 (5), 683–690. Longley, M., Jepson, P.C., Izquierdo, J., Sotherton, N., 1997. Temporal and spatial changes in aphid and parasitoid populations following applications of deltamethrin in winter wheat. Entomol. Exp. Appl. 83, 41–52. Mamood, A.N., Waller, G.D., 1990. Recovery of learning responses by honeybees following a sublethal exposure to permethrin. Physiol. Entomol. 15, 55–60. Masuda, K., Ihara, M., Nishimura, K., Sattelle, D.B., Komai, K., 2001. Insecticidal and neural activities of candidate photoa?nity probes for neonicotinoid binding sites. Biosci. Biotechnol. Biochem. 65 (7), 1534–1541. Padilla, S., 1995. The neurotoxicity of cholinesterase inhibiting insecticides: past and present evidence demonstrating persitent e?ects. Inhal. Toxicol. 7, 903–907. Pettersson, J., 1970. An aphid sex attractant. Ent. Scand. 1, 63–73. Rafalimanana, H., Kaiser, L., Delpuech, J.M., 2002. Stimulating e?ects of the insecticide chlorpyrifos on host searching and infestation e?cacy of a parasitoid wasp. Pest Manag. Sci. 58, 321–328. Salerno, G., Colazza, S., Conti, E., 2002. Sub-lethal e?ects of deltamethrin on walking behaviour and response to host

627

kairomone of egg parasitoid Trissolcus basalis. Pest Manag. Sci. 58, 663–668. Salgado, V.L., 1997. The mode of action of spinosad and other insect control products. Down Earth 52 (1), 35–44. Sandoz, J.C., Laloi, D., Odoux, J.F., Pham-Delgue, M.H., e 2000. Olfactory information transfer in the honeybee: compared e?ciency of classical conditioning and early exposure. Anim. Behav. 59, 1025–1034. Soderlund, D.M., Bloomquist, J.R., 1989. Neurotoxic actions of pyrethroid insecticides. Annu. Rev. Entomol. 34, 77–96. Sss, L., 1983. Survival of pupal stage of Aphidius ervi Hal. in u mummi?ed Sitobion avenae F. to pesticide treatment. In: Cavalloro, R. (Ed.), Aphid Antagonists. Balkema, Rotterdam, pp. 129–134. Taylor, K.S., Waller, G.D., Crowder, L.A., 1987. Impairment of a classical conditioned response of the honey bee (Apis mellifera L.) by sublethal doses of synthetic pyrethroid insecticides. Apidologie 18 (3), 243–252. Van Driesche, R.G., Bellows, T.S., 1996. Biological Control. Chapman and Hall, New York. Vandame, R., Meled, M., Colin, M.E., Belzunces, L.P., 1995. Alteration of the homing-?ight in the honey bee Apis mellifera L. exposed to sublethal dose of deltametrhin. Environ. Toxicol. Chem. 14 (5), 855–860. Venables, W.N., Ripley, B.D., 1999. Modern Applied Statistics with S-Plus. Springer-Verlag, New York. Vet, L.E.M., Van Lenteren, J.C., Heymans, M., Meelis, E., 1983. An air?ow olfactometer for measuring olfactory responses of hymenopterous parasitoids and other small insects. Physiol. Entomol. 8, 97–106. Vinson, S.B., 1998. The general host selection behavior of parasitoid Hymenoptera and comparison of initial strategies utilized by larvaphagous and oophagous species. Biol. Control 11, 79–96.


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